There is known a valve timing adjusting device that can adjust valve timing of an intake valve and an exhaust valve of an engine. For example, a valve timing adjusting device in JP-A-2003-120231 includes a housing that can rotate integrally with a crankshaft, and a vane rotor that can rotate integrally with a cam shaft, and changes pressures of an advance chamber and a retard chamber in the housing to relatively rotate the vane rotor, thereby adjusting the valve timing. When the advance chamber and the retard chamber are not distinguished from each other, they are hereinafter referred to as an “oil pressure chamber”.
Pressure control of the oil pressure chamber is performed by a direction switching valve provided for, for example, a cylinder head of the engine. This direction switching valve supplies operating oil, which has been pressure-fed from an oil pump, into the oil pressure chamber through an oil passage of the cylinder head and an oil passage of the cam shaft. In JP-A-2003-120231, a filter is provided between the oil pump and the direction switching valve. Foreign substances contained in the operating oil pressure-fed from the oil pump are captured by this filter.
In JP-A-2003-120231, the operating oil flowing out of a discharge port of the direction switching valve is supplied into the oil pressure chamber through the oil passage of the cylinder head and the oil passage of the cam shaft. Thus, the foreign substances contained in the above oil passages may enter into the oil pressure chamber. Particularly, at a connection part between the oil passage of the cylinder head and the oil passage of the cam shaft, there is a bearing part of the cylinder head for rotatably supporting the cam shaft. Accordingly, worn powder produced at this bearing part may enter into the oil pressure chamber.
Against this, there may be taken a measure to provide the direction switching valve at an oil passage of the vane rotor and to provide the filter at a supply port of the direction switching valve. Therefore, the direction switching valve and the filter are provided inside the valve timing adjusting device. As a result, the foreign substances in the oil passage of the cylinder head and the oil passage of the cam shaft can be captured by the filter.
However, in a mode where a check valve is provided on an upstream side of the direction switching valve to prevent a backflow of the oil supplied to the oil pressure chamber, if the filter is provided at the supply port of the direction switching valve as described above, the foreign substances pass through the check valve. Consequently, the check valve may not be closed because of the foreign substance lodging between a valving element and a valve seat of the check valve.